This invention relates to a communication antenna and in particular it is concerned with a communication antenna for a mobile phone.
Known antenna for a mobile phone consist of a helix with or without a radiating straight element. The helix serves to provide for radial radiation/reception. However some energy is lost as circular polarised radiation along the axis of the xe2x80x98helicoilxe2x80x99 section.
According to a first aspect of the present invention there is provided a communication antenna having a driven element extending between a feed point and an attachment point to a top loaded element characterised in that the driven element is longer than the distance between the feed point and the attachment point.
According to a first preferred version of the first aspect of the present invention the driven element is configured to follow a meandering path between the feed point and the attachment point.
According to a second preferred version of the first aspect of the present invention or the first preferred version thereof the driven element is at least in part in the form of straight sections joined to give a zigzag configuration.
According to a third preferred version of the first aspect present invention or the first preferred version thereof the driven element is at least in part in the form of curved sections.
According to a fourth preferred version of the first aspect of the present invention or any preceding preferred version thereof the driven element is of a predetermined length relating to operating frequency band and return loss requirements.
According to a fifth preferred version of the first aspect of the present invention or any preceding preferred version thereof the antenna is equipped with at least a pair of parasitic elements the members of the pair being disposed on either side or on opposite sides of, and off-set from, the driven element and parallel or slant to a straight line linking the feed point to the attachment point; the parasitic elements serving to provide impedance matching and increased bandwidth and providing shielding against radiation from the antenna in a predetermined direction. Typically passive elements are incorporated parasitic elements to provide for an overall reduction in the size of the antenna.
According to a second aspect of the present invention there is provided a mobile phone incorporating an antenna according to the first aspect or any preferred version thereof.
According to a first preferred version of the second aspect of the present invention the antenna is formed as a printed circuit board or is deposited on a laminar member having a structural function for at least a part of the phone.
According to a second preferred version of the second aspect of the present invention or the first preferred version thereof the parasitic elements are disposed relative to the driven element to provide increased bandwidth and shielding against radiation from the antenna in a predetermined direction such as towards a user of the phone or at least towards the nearest part of a user of the phone.